1. Field of the Invention
This invention relates to heating and cooling systems, and, more particularly, to heating and cooling systems having both evaporative coolers and heat pumps connected to a common duct system, including the use of evaporative cooling as a precooler for a condenser and the use of evaporative cooling for an attic, all from a single system utilizing movable dampers in a duct system.
2. Description of the Prior Art
Evaporative cooling systems are old and well known in the art. They utilize the heat of vaporization for cooling air. Ambient air is simply drawn through water soaked pads. The hot, low humidity outside air is cooled by giving up heat to evaporate the water on the pads. The cooled air has its humidity increased in the process. Such systems have their drawbacks in that there must be a continuous supply of fresh, warm (hot), and relatively dry (low humidity) air. Moreover, the building in which the system is used must be able to handle the supply of incoming air, and that requires some type of ducting of the air out of the structure, to be returned to the outside air.
Another disadvantage of evaporative cooling systems is the substantial increase in the humidity within the structure during the time of operation of the evaporative cooling system. Along with this disadvantage, it is obvious that if the air supplied to the evaporative cooling system has a high relative humidity, the functioning of the system is decreased. In other words, as the relative humidity of the ambient air increases, the efficiency of the cooling system decreases.
Heat pumps are also well known and understood in the art. A heat pump is a system with a reversible cycle for both heating and cooling. For cooling purposes, the heat from the air is exchanged by the heat pump apparatus and a cooling of the air results. For heating purposes, heat is extracted from the air (outside air) and the heat from the outside air is used to raise the temperature of inside air. When the supply (outside) air is relatively cool, the heat is supplemented by utilizing an additional source, such as an electric resistance heater.
In the cooling mode, the heat pump is similar to a refrigeration system, and it has substantially the same components. However, a refrigerator or refrigeration system extracts heat from a chamber by the evaporation of a refrigerant, and thereby reduces the temperature of the air in the chamber, while the heat pump utilizes the condensation of a heat transfer medium. The primary difference between heating and cooling in the heat pump is in the coils referred to as the condenser and the evaporator. In the heating mode, heat is added to the air by being blown over condenser coils and circulated through the structure. The air which passes over the evaporator is accordingly outside air, which gives off heat through the evaporator.
In the cooling cycle, inside air is circulated through the evaporator, where the heat is given off and thus cooled air is recirculated through the structure. The outside air is circulated through the condenser to cool the condenser. A four-way valve is used to switch between the heating and cooling cycles.
In recent years the efficiency of refrigeration systems for homes, and the like, has been increased by cooling the condenser coils in a more efficient manner. For accomplishing this, units referred to simply as pre-coolers have been used. These pre-coolers simply provide a spray of water directly onto the condenser coils. The heat given off by the condenser coils is accordingly transferred to the water and the air. Such apparatus are shown in U.S. Pat. Nos. 3,427,005 and 3,108,451.
For improving the efficiency of the use of energy, particularly for the southwestern portion of the United States, the combining of heat pumps with evaporative cooling systems has been suggested. Such apparatus is shown in U.S. Pat. No. 3,859,818. In the '818 patent, a refrigeration air conditioner and an evaporative cooler air conditioner use the same ducts to supply conditioned air throughout a building, such as a home. Both the supply duct and the return air duct for the refrigeration (heat pump) system are used as a single supply duct for the evaporative cooler.
U.S. Pat. No. 3,182,718 discloses a combination of an evaporative cooling system, a heater, a refrigeration system, all of which operate using a single blower for moving air. A plurality of dampers or louvers is connected to a duct system to allow a single blower to be used for all three devices.
U.S. Pat. No. 4,066,118 discloses a combination of a heat pump with facilities for thermostorage, an evaporative cooler, and a solar heat collector. The heat pump uses two heat exchangers, an indoor heat exchanger and an outdoor heat exchanger, and a third heat exchanger in series with the outdoor heat exchanger, with the third heat exchanger used to provide heating or cooling, as required by the heat pump, during critical ambient conditions. The third heat exchanger is used to improve the relative efficiency of the heat pump under certain critical conditions.